7-Zip

License

7-Zip is free software with open source.
The most of the code is under the GNU LGPL license.
Some parts of the code are under the BSD 3-clause License.
Also there is unRAR license restriction for some parts of the code.
Read 7-Zip License information.

You can use 7-Zip on any computer, including a computer in a commercial organization.
You don't need to register or pay for 7-Zip.

Compression ratio results are very dependent upon the data used for the tests.
Usually, 7-Zip compresses to 7z format 30-70% better than to zip format.
And 7-Zip compresses to zip format 2-10% better than most of other zip compatible programs.